Well it will take a long time to copy but shouldn't damage your PC,you could copy it in bits so like 100 GB a day say cause it could slow down your PC from being able to do anything else,depending on what your PC is and its CPU,and how fast it is.
One big thing with Windows that slow it down is hard drive activity. Watch Windows 10 at boot up how long it takes of it to stop accessing the hard drive and slowing the PC down.